Methods and systems for measuring, displaying and recording time-rate of penetration

ABSTRACT

The provision of means to measure, display and record the rate of a boring bit penetration during a drilling process by measuring the movement of the bit supporting cable and interpreting said measurement to include the time of the penetrating movement of the bit and thereafter displaying and recording said time rate of penetration of said bit.

"i3 151e5 5R 12 1C1 7 1- OR 33853 3004 0 i i United States Patent 1 11111 3,853,004

Westlake et al. [451 Dec. 10, 1974 METHODS AND SYSTEMS FOR 3,312,828Q4/1967 Wingate 250/233 x MEASURING, DISPLAYING AND 3 32 g w 3 1 3, l 7,mit eta 4018 RECORDING TIME'RATE 0F 3,364,359 H1968 Cronin 250 231 s15PENETRATION 3,364,494 l/l968 Dellinger et a]. 346/30 [75] Inventors:John Henry Westlake; John Wallace fif g ag 1 er e a.

22x1? ggig g gri gfi 3;??? 3,522,727 8/1970 Calhoun 73 1515 3,541,85211/1970 Brown et al. 73/1515 x Calgary Alberta, Canada 3,620,077 11/1971Brown et al. 73/1515 73] Assigneez Eastman Oil We Survey Company,3,643,504 2/1972 Rundell 73/l51.5 Houston, 3,651,871 3/1972 Greene173/21 [22] Filed: 1971 I Primary Examiner-Jerry W. Myracle [21] App].NO; 190,881

[57] ABSTRACT 52 U.S. c1. 73/1515, 33/125 B The Provision of means tomaasure, display and 51] Int. Cl E21b 45/00 cord the rate of a boringbit Penetration during a dril- [58] Field of Search 73/1515; 33/125 B;ling Process by measuring the movement of the bit 340/345; 250/231 SEsupporting cable and interpreting said measurement to include the timeof the penetrating movement of the [56] References Ci d bit andthereafter displaying and recording said time UNITED STATES PATENTS rateof penetration of said bit.

2,98l,l02 4 1961 Melton 73/1515 2 9 l im 12 Drawing Figures 3 SYSTEMINPUT READ-HEAD ANALOG STRIP-CHART RECORDER ELECTRONICS 1mm 5 Flume:

BMPAL READ-OUT PATENTED DEC 10 I974 SHEET 1 OF 7 528mm HES 835 R @Q BEE252w m PATENHED DEC 10 I974 3.853.004 SHEEI 20F 7 mm mi UN 3k PAIENTEUDEC 10 19w SHEET 5 0F 7 'RTER FROM INVL mum LQQK R V swam:

BUFFER AMP 8c nrrsmm'mn GREEN I LAMP (JCT.

R s 10 man LIGHT 2: 0m CIRCUIT FROM nmsc'r SHAFT CLOCK To 3120 sncomzn#31 1,0010 FROM 1.10m INVERTER PUS}1 BUTTON CIRCUIT cmcum 10 coummz R/SIIICREMENTER T c1 {CUIT #5 F/F# FROM D5130? SHAFT PUSH-BUTIm-I ENCODER#5 cmcun' DETECT #70 courwsn #1 FROM DIVIDB SHEBNFT LEADING EDGEDIFFERENTIATE TRAILING EDGE DIFFERENTIATE SIGNAL COMMAND ING "TRANSFERCONTENTS OF COUNTER #2 TO BUFFER MTCIES" 'sxmm. COIMANDING "CLEARcounrmi #2" BUFFER FROM AMPLIFIER COUNTER #1 F/F 5 SWITCH p DIFFER- MONOOUTPUT murmon 53 METHODS AND SYSTEMS FOR MEASURING, DISPLAYING ANDRECORDING TIME-RATE F PENETRATION This invention relates to methods andsystems for the uni-directional measurement, display and recording, in aphysical operation, of the time rate of movement of a first elementrelative to a second element in contact therewith, where a first of saidelements is progressively diminished at the contact interface bypenetration, erosion, drilling or other form of consumption by thesecond of said elements.

More particularly, the present invention has general application inindustrial process work, and has a specific application in boring bitpenetration in a well drilling operation, which specific applicationwill hereinafter in this specification be described in detail, it beingunderstood that such illustrates merely by Way of example, a preferredform of the methods and systems for the practise of the invention.

In the field of sub-surface petroleum exploration, a bore-hole may bedrilled into the earth by means of a mechanical drilling rig thatsupports, and causes to rotate, a drilling stem having a boring bitaffixed to its lower end. As the bore-hole is drilled deeper into theearth, the drill stem may be lengthened by the addition of sections atthe surface.

A typical rotary drilling rig includes a floor mounted disc having asquare hole at its centre. While drilling is in progress, this disc iscaused to rotate by the rigs main source of mechanical power. The squarehole in the disc loosely accommodates a steel shaft colloquially knownas a kelly. The kelly, free to move through the hole in the disc, andbeing of square cross section, rotates with the disc.

The lower end of the kelly is connected to the circular cross sectiondrill stem, while its upper endis connected to a swivel joint in themoveable bottom block of a block and tackle system. The top block of thesystem is affixed to the rig superstructure (the crown of the derrick).A steel cable, run-from a drum driven by the rigs main source ofmechanical power, is threaded through the sheaves of the upper and lowerblocks. The net effect is to provide a means of raising and lowering therotating drill stem.

During the drilling operation, a fluid colloquially known as mud" isforced down the hollow drill stem, through the bit, and back to thesurface through the annulus between the stem and the walls of theborehole. The purpose of the drilling fluid is to carry the bit cuttingsto the surface and to provide lubrication and cooling of the bit.

The main factors that contribute to the efficiency of the drillingoperation are; the physical condition of the bit, the rate of bitrotation, the weight placed upon the bit, the viscosity of the drillingfluid, and the rate at which this fluid is circulated. Of these, theonly factor that cannot be determined directly, at the surface, is thephysical condition of the bit. One common drilling method is to use aconstant weight and rate of rotation, then monitor the rate at which theborehole progresses. A decreasing penetration rate may indicatedeterioration of the bit, but the stratified nature of the subsurfacemay confuse the issue. For example, if the bit progresses from onegeological formation to another, wherein the transition is to a moredifficult material, it may appear to the driller that the bit hasdeteriorated to the point at which it must be replaced. Replacing thebit is an expensive, time consuming operation because the entire drillstem must be raised, with sections being stacked as they are pulled fromthe earth, until the bit reaches the surface.

In an attempt to minimize this problem, logs describing the sub-surfacegeology of adjacent completed wells are often consulted. If the changesin earth structure can be predicted with reasonable accuracy, thechanges in penetration rate may be justified, and a bit may not bechanged until it is, in fact, unserviceable.

Further, the influence of one variable upon another contributes to theart of well drilling in that, for example, increasing the weight on thebit and/or its rate of rotation may or may not increase the rate of bitpenetration.

From the foregoing, it is apparent that the rate at which the boreholeprogresses is an extremely important parameter in the drilling process.

In the present state of the art, drilling rate is measured as a functionof time (ie: the time it takes to drill, say, 1 foot). Thesemeasurements are subsequently processed mentally, mechanically orelectronically, to establish the rate of penetration in engineeringunits of velocity. From the standpoint of the driller, a presentation ofthe time required to drill one foot can be confusing in a dynamicoperation. Further, to permit a subsurface Geologist to correlate therate of penetration with logs from adjacent wells, time consuminginterpretation of time based information is required. This is becausethe logs are not functions of time but functions of depth ofpenetration.

It is an object of this invention to provide new and improved methods ofmeasuring, displaying and recording the time rate of boring bitpenetration in engineering units of velocity, wherein the recordingpresents time rate of penetration versus depth of penetration ratherthan versus time.

It is another object of this invention to provide a means wherebydrilling rate information may be electronically telemetered to a distantlocation, such information being in a Binary Coded Decimal format.

In accordance with one feature of this invention, the average time rateof bit penetration, over. each sequential thirty second time interval,is presented to drilling personnel in the form of an illuminated digitalin-line read-out in feet per hour (or other velocity units such asmeters/hour, inches/second, cm/second, etc.).

In accordance with another feature of this invention, an analog recordis produced wherein the abscissa is depth of penetration in feet, andthe ordinate is rate of penetration in feet per hour (or other velocityunits if required).

In accordance with another feature of this invention, no moving cablelink is required between the moving block or swivel joint and thefacilities on the floor of the drilling rig.

In accordance with another feature of this invention, the measuringsystem automatically shuts down when the stem is raised, so that thereturn trip to the bottom of the hole is not presented as indicative ofdrilling rate. This feature also applies to the up and down motion ofthe stem supporting mechanism attendant upon the addition of lengths ofdrill stem.

In accordance with another feature of this invention, mechanicalvibration and/or random vertical motion of the'drill stem will not beaccepted as valid -rate of penetration data. This also applies to thedrill stern supporting mechanism in cases where the two aredisconnected.

In accordance with another feature of this invention, drilling rate dataare made available in both parallel and serial digital forms forsubsequent processing and- /or telemetering.

In accordance with another feature of this invention, extremely smallincrements (EG: tenths of an inch) of depth of penetration can bedetermined over fixed time intervals.

In accordance with another feature of this invention, the electronicscircuitry is exclusively solid state to provide the rugged, dependableoperation required in the drilling rig environment.

In accordance with another feature of this invention, the system isself-calibrating in that, on start up, the position of its inputtransducer is of no significance.

AN OVERVIEW OF THE METHOD AND A TYPICAL SYSTEM The system comprises aremote system input head, an electronics main frame, a remoteelectronics digital read-out unit, and a remote analog strip chartrecorder having depth of penetration on its abscissa and time rate ofpenetration on its ordinate.

The remote input head comprises a rotatable wheel and electronicscircuitry that, by means of an optically coupled shaft position encoder,is capable of transmitting Binary Coded Decimal information down thederrick to the electronics main frame located in the drillers cabin(colloquially known as the dog-house). The input head is installed, bymeans of a springloaded bracket, such that its rotatable wheel is placedin intimate contact with either the draw works cable as it passes overone of the upper block sheaves, or with a sheave itself. Which of thecable/sheave contacts is used will dictate the circumference of therotatable wheel. For example, the cable over the slow sheave moves attwice the drilling rate; Assuming that the present systems driving wheelis caused to rotate by the cable over the slow sheave or by the slowsheave itself, to present the contained shaft position encoder with a 1foot of penetration per revolution input, the driving wheel must be 2feet in circumference.

Parallel BCD data are transmitted via a multi pair cable down thederrick to the instrument main frame. This main frame contains powersupplies and solid state electronics logic circuitry. Power is suppliedto all subsystem assemblies by the main frame, and its logic circuitryprocesses data representative of amount of penetration into datarepresentative of time rate of penetration.

Two read-out units are provided. One of these is an illuminated digitalin-line read-out and the other is an analog strip chart display. Thedigital read-out unit may be placed at a reasonable distance from themain frame in a location convenient to the driller, and it presents theactual drilling rate in, say, feet per hour, updated every (for example)seconds. The analog strip chart recorder has a chart paper drivemechanism that incrementally steps the chart in response to depth ofpenetration, while its pen traces the rate of penetration in velocityunits. By means of a switch on the main frame, the user may select anyofa number of full-scale deflections applicable to the strip chartrecord. For example, if drilling is slow, he may choose a full-scalerecorder deflection of 25 or 50 feet per hour; if drilling is relativelyfast, he may select a full-scale deflection of 200 feet per hour.Another switch on the system main frame permits the user to select anintegrating time constant for the strip chart recorder that effectivelysmoothes out the analog record. If he wants maximum detail in the analogrecord, he selects the lowest integrating switch position. If he prefersto sacrifice detail for over-all clarity with respect to correlation oflogs from adjacent wells, he selects a higher integrating time constantthat removes the peaks of the record and averages the readings. Stillanother switch on the main frame permits the user to select any of anumber of abscissa weightings for the strip chart record. He can select,for example, any of 5, 10, 2O, 40, or inches of chart paper per feet ofpenetration.

The digital display unit, in presenting drilling rate in feet per hourupdated every 30 seconds, is telling the driller how many tenths of aninch he drilled during the immediately preceding 30 second timeinterval. An optional printer/totalizer may be connected to the digitalread-out unit that will provide a print-out and new total every 30seconds. For example, sequential readings of 31, 36, 27 and 24 feet perhour (total 118) means that 11.8 inches of drilling was accomplishedduring this particular 2 minute time interval.

An important feature of the present invention is its immunity toerroneous drilling information caused by mechanical vibrations and theoccasional raising of the lower block (EG: to add lengths of drillstem). If the driller raises the kelly for any reason, the presentsystem automatically shuts down and illuminates a red lamp on thedigital read-out unit. When the driller resumes drilling, he presses aRESET button on the digital read-out unit, and the system re-commencesoperation. Without this feature, the system would interpret mechanicalvibratory motion, and the lowering of a new section of drill stem, asindicative of downward motion of the bit. Incidentally, a green lamponthe digital read-out unit informs the driller that the system isoperational.

Another important feature of the present invention lies in its automaticself-calibrating capability. On startup, the angular position of therotatable wheel, and its affixed transducer, is of no consequence to thesystem.

An optional feature in the present invention is electronics circuitrythat serializes and identities drilling rate data for presentation to adigital telemetry link. This provides the user with a means oftransmitting accumulated data over telephone lines and/or wirelesslinks.

DETAILED SYSTEM DESCRIPTION For a better understanding of the presentinvention, together with other and further objects and features thereof,reference is made to the following description taken in conjunction withthe drawings in which:

FIG. 1 illustrates the various assemblies comprising the presentinvention,

FIG. 2 illustrates the components comprising the READ-HEAD,

FIG. 3 is a block diagram illustrating one arrangement of circuitry inthe present invention,

FIG. 4 illustrates the logic diagrams of COUNTER number I and theCOMPARATOR,

FIG. 7 illustrates, in block form, the COUNTER IN- CREMENTER circuit,

FIG. 8 illustrates, in block form, the READ -IN COMMAND and COUNTERCLEAR circuit,

FIG. 9 illustrates, in block form, the analog recorder PAPER ADVANCEcircuit.

Referring to FIG. 1: In a typical drilling rig arrangement, the cable(I) from the draw-works is threaded through a number of sheaves in apair of blocks, the lower of which supports a swivel joint, a kelly, andthe drill stem. The movement of the cable over the slow sheave (2)occurs at twice the rate of actual bit penetration.

The present invention provides a READ-HEAD (3) whose input drum isintended to make physical contact with the existing cable over the slowsheave, or with the slow sheave itself, and hence rotate in sympathywith an axial movement of this cable.

A multi pair electrical cable (4) is affixed at its upper end to theRead-Head by means of an adequate male/- female electrical connector,and at its lower end, via a similar electrical connecting means, to thesystem MAIN FRAME (5), usually located in a convenient place in. therigs operating area. The electrical cable is run from theread-head (atthe derrick crown) down a leg of the derrick (affixed thereto by meansof spaced cable clamps) to the main frame.

The main frame contains the means whereby the data provided by theread-head are electronically processed for subsequent presentation tothe DIGITAL READ- OUT UNIT (6) and the ANALOG STRIP CHART RE- CORDER(7). The main frame also contains panel switches to permit the user toselect integrating time constants, abscissa weightings, and full-scaledeflection factors for the analog strip chart recorder.

Referring to FIG. 2: The READ-HEAD comprises a cylindrical housing (8)in which there is axially mounted a rotatable assembly consisting of areading drum (9) intended to make contact with the drawworks cable overthe slow sheave or the slow sheave itself, said drum being rigidlyaffixed to a shaft (10), which is supported at the ends of the housingby means of bearings (11). Rigidly affixed to the said shaft is anoptical shaft position encoder (12) having two Binary Coded Decimalsequences, each representing decimal l to 60. The shaft position encoderis shown in more detail in FIG. 2(B). Rigidly affixed to the saidhousing is a group of six Gallium Arsenide light emitting diodes (orincandescent lamps) (13), arranged so that each is aligned with one ofthe six binary levels contained in the shaft position encoder. On theother side of said shaft position encoder, there is a stack" of sixlight sensitive photo transistors (14), each aligned with itscorresponding light source through the applicable levels of the BCDshaft position encoder. Each of the said photo transistors is mounted ona DECODER circuit card (15) that also includes amplifying and pulseshaping electronics circuitry. One circuit to accomplish the desireddecoding, amplifying and shaping is shown in FIG. 2(C). Here, the phototransistor (16), under the influence of random light or light directedby the shaft position encoder (it) produces an output detectable by thedifferential amplifier (17), that is biased to reject noise caused byrandom light, and amplify signals caused by light directed by clearspaces in the shaft position encoder. Signals are squared by the Schmitttrigger circuit (18), amplified by the buffer amplifier (19), andpresented as'an output U (in the case of the phototransistor/electronics card in the least significant bit position of theshaft position encoder). The output signal U is also inverted by meansof a unity gain logic inverter (20) to present a second output U. Withsix identical cards, the pairs of data outputs U,U; V,V; W,W; X5; YY;and Z? are available to indicate the presence and absence of signalsseen in each data word by the particular alignment of the shaft positionencoder.

The overall effect of the read-head assembly, then, is to detect axialmotion of the rigs draw works cable, and, by means of an opticallycoupled shaft position encoder, present adequately shaped and amplifieddigital data words to the system main frame. Incidentally, the cableused to transmit the data words to the main frame also carries the powerto the read-head.

It should be noted that the circuit shown in FIG. 2(C) is but oneapproach to he data reporting technique. An alternative circuit can beused in which the differential amplifier and the Schmitt trigger arereplaced by a single operational amplifier.

Referring to FIG. 3: When the system is energized, pulses from the clock(17) are fed to COUNTER number l (18) via the COUNTER PRE-SET AND AUTO-MATIC SHUT-DOWN (l9) and COUNTER INCRE- MENTER (20) circuits. Meanwhile,the random angular position of the binary coded shaft position encoderpresents an arbitrary data word to the photo transistor decoders (14 &15 FIG. 2), which is then transmitted to the COMPARATOR (21) in paralleldigital format. As COUNTER number 1 accepts and counts clock pulses,sooner or later the contents of this counter will coincide with theinput data word, and the coincidence is detected by the COMPARATOR. Theresulting output from the comparator disables the clock feed to counternumber 1, and illuminates the green lamp on the REMOTE DIGITALREAD-OUT'UNIT (22) to signify that the system is synchronized" inpreparation for drilling rate input data. Thisprimary coincidence alsofeed a pulse to counter number 1 that increases the contents of thiscounter by 1. At this point, counter number 1 contains a number onelarger than the current data word from the photo transistors. If theshaft position encoder is now rotated clockwise (the directionindicative of bit penetration), the next data word seen by thecomparator will coincide with the data word held in counter number 1,causing another output pulse to be generated by the comparator. Thisoutput pulse updates counter number 1 by 1, and also enters COUNTERnumber 2 (23) as a valid count. This sequence of events is repeated foreach data word/counter number 1 coincidence. Counter number 1 iscompatible with the input data words, since it is designed to count from1 to inclusive, then re-set to l and repeat its counting cycle.

If the shaft position encoder rotates counterclockwise, due to vibrationand/or an upward motion of the stem supporting mechanism, the next wordpresented to the comparator by the photo transistors will be two lessthan that stored in counter number I; no coincidence will exist, nopulse will be fed to counter number 2, and no increase in counter number1 occurs. If

the reverse rotation continues beyond the design limit for vibratorymotion (EG: if the drilling block is raised to add a length of drillstem), the system will recognize, as will be shown later, that following59, the counting sequence reaches 31 before it reaches 30, and shutdownoccurs. The shut-down event extinguishes the green lamp on the digitalread-out panel, and energizes the adjacent red lamp, informing theoperator that he must press the re-set button to obtain furtherreadings. The start-up procedure described above is activated by there-set button.

Because of the arbitrary angular position of the shaft position encoderwhen an excessive reverse motion occurs, and recognizing that there aretwo 1 to 60 counting sequences per foot of cable movement, and since thereading must pass 59 before shut-down occurs on 31, it follows that thedesign limit for reverse travel is not less than 3 inches and not morethan 6 inches.

In accordance with the earlier description of properly sequenced forwardreadings, counter number 2 accumulates a count of the number of timescoincidence occurs in the comparator. The contents of counter number 2,over fixed time intervals, is a measure of the rate of clockwise shaftposition encoder rotation, and

hence represents the velocity of boring bit penetration during the welldrilling operation.

To preserve the continuity of readings, the system includes transfer andstore circuitry in association with counter number 2. Here, at the endof each 30 second time interval, parallel (or jam) transfer is effectedfrom counter number 2 to a BUFFER REGISTER (24) consisting of electroniclatching switches. This frees the counter to accumulate the next readingwhile the current reading is presented as a digital read-out thatpersists for 30 seconds. At the end of this 30 second time interval, thenew counter number 2 reading is transferred to the buffer registerdisplacing the previous reading, the digital read-out is momentarilyextinguished then presented with the new contents of the bufferregister. Counter number 2 is then cleared and immediately beginscounting coincidences in the next 30 second time interval. This providescontinuous readings, updated every 30 seconds, of the drilling velocityin feet per hour.

Counter number 2 consists of 12 Flip Flops connected to provide a threedecade counter. Each decade contains four flip flops and standard countof ten feedback circuitry. The contents of this counter, then, isrecognizeable as hundreds, tens, and units, available in simultaneous orparallel output.

The 30 second time intervals are derived from the built in clock. Thisclock is an oscillator designed to produce 8.54 pulses per second. Thesepulses are fed to the DIVIDE BY 256 COUNTER (25), which consists ofeight series connected flip flops. When this counter resets to zero(when 256 pulses have been received from the clock), an output pulse isgenerated by the flip flop in the Most Significant Bit position. With8.54 pulses per second divided by 256, the output from this counter is 1pulse per seconds. Every 30 seconds, then, a rectangular pulse is fed tothe READ-IN COMMAND AND COUNTER CLEAR circuit (26). In this circuit, theleading edge of the pulse is differentiated, amplified and then used totransfer the contents of counter number 2 to the buffer register. Thetrailing edge of the pulse is also differentiated and amplified toprovide a pulse that clears counter number 2. This means that every 30seconds the contents of counter number 2 are jam transferred to thebuffer register for holding and simultaneous digital read-out, and thecounter is cleared inpreparation for the next count.

Each comparator sequential coincidence represents 1/120 shaft encoderrevolution. Since one revolution of the shaft encoder represents 1 footof bit penetration (consistent with the diameter of the driving wheel),and remembering that there are -30 second time intervals per hour, itfollows that the number of coincidences detected in each 30 second timeinterval is a measure of the rate of bit penetration in feet per hour,and also a measure of the number of tenths of an inch drilled in the 30second interval. The contents of counter number 2, then, requires nomathematical treatment prior to readout.

The DIGITAL TO ANALOG CONVERTER (27) accepts 12 inputs from the bufferregister and presents a single analog voltage representative of thedrilling rate in feet per hour. This is accomplished through the use ofstandard electronics circuitry 12 buffer amplifers, twelve electronicswitches, 12 precision resistors in a BCD ladder, and a singleoperational amplifier). The output from the digital to analog converteris presented to the RECORDER PEN DRIVE circuit (28) through anINTEGRATOR (29) and a FULL SCALE DE- FLECTION SELECTOR (30).

The analog recorder, as previously mentioned, accommodates depth ofpenetration on the abscissa and time rate of penetration on theordinate. The integrating circuit provides a means of selecting theordinate time constant such that the rate of penetration readings can beaveraged, over selectable time intervals, prior to presentation to therecorder pen-drive mechanism. The scale selecting circuit provides anumber of choices in the value of drilling rate informationrepresentative of full-scale deflection of the recorder pen.

The chart paper abscissa advancing mechanism (31 in the analog recorder,is a relay/escapement device responsive to depth of penetration pulsesobtained from counter number 1. In effect, as the depth of the bore holeprogresses, the strip chart papaer is incrementally advanced while itspen traces the rate of bit penetration on the ordinate.

A BCD SERIALIZER (32) is available as an optional feature. This circuitconsists of a 12 bit shift register into which the contents of thebuffer register are periodically dumped. Separately derived clock pulsesthen shift the contents of the register, sequentially, into a MODEMsystem with control and identification bits being added as required.

There follows a more detailed description of selected electronicscircuitry comprising the system.

Referring to FIG. 4: The (A) sketch is a simplified block diagram ofcounter number 1. Here it is seen that this counter contains six seriesconnected flip flop circuits labelled A to F inclusive. Standardfeed-back circuitry (not shown) provides a counting scale from decimal 1to decimal 60, such that the 61st input pulse clears the counter andsets the A flip flop to its 1 state. The net operation, then, provides al to 60 counter that continually repeats this cycle as pulses arereceived at its input. Each flip flop in counter number 1 has twooutputs (labelled AK; BE; etc.) to give a positive indication of whetherthe flip flop is in its 0 or 1 state. The A flip flop represents theleast significant bit in the counting sequence.

Again in'FIG. 4, the (B) sketch shows the logic arrangement of thecomparator. This circuit consists of 12 2-input positive NAND gates, six2-input negative NOR gates, and one 6-input positive NAND gate. A to Finputs are provided by counter number I, while the photo transistordecode units (FIG. 2(C)) provide inputs U to Z. The function of thelogic is to produce an output if, and only if, the six bit word from thephoto transistors is identical to the six bit word held in counternumber I. If, for example, the two words differ only in their leastsignificant digits, there will exist AU and AU at the inputs to the LSDNAND gates, and neither of these gates will be enabled. The NOR functionwill not be satisfied, so no input appears at the applicable six inputNAND gate position, and no comparator output is generated.

Referring to FIG. On start-up, the operator presses the RESET button onthe remote digital read-out unit, and clock pulses will appear in theoutput of this circuit. This is because Reset/Set Flip/Flop number Ienables NAND gate number I, and R/S F/F number 2 is high (switched bythe push-button), enabling NAND number 2. Counter number I, then,receives and counts pulses (through a COUNTER INCREMENTER circuit) foras long as NAND number I is enabled and R/S F/F number 2 is in the highcondition. When counter number 1 reaches coincidence with the randomnumber seen by the photo transistors, an output is generated by thecomparator in the form of a negative going pulse. This pulse enters theBUFFER AM- PLIFIER & INTEGRATOR, which feeds LOGIC IN- VERTER number 1with a trapezoidal positive going pulse. The output of logic inverternumber I is a somewhat lengthened version of the comparator outputpulse, and has a slight time overlap. This pulse switches R/S F/F numberI, disabling NAND number 1, and clock pulses are blocked from theoutput. Logic inverter number 1 also feeds a MONOSTABLE MULTI- VIBRATORthat stretches and inverts the pulse. The Sl-IAPER is a trailing edgedifferentiator that produces a short negative going pulse that issignificantly delayed with respect to the output of the comparator. Anoutput is produced, then, whenever a coincidence is detected by thecomparator, providing R/S F/F number 2 is in the high condition. Theclock feed through NAND number I is disabled for as long as R/S F/Fnumber ls output is low.

In the AUTO SHUT-DOWN portion of the circuit, R/S F/F number 2 will beswitched to the low condition if, after enabling of the DETECT SHAFTENCODER number 59 NAND gate, DETECT SHAFT ENCODER number 31 is enabledprior to DETECT number 30 COUNTER number I. This is because thedetection of number 59 on the shaft encoder causes R/S F/F number 3 topresent a high condition to NAND number 3, and if number 31 on the shaftencoder is detected prior to number 30, both inputs to NAND number 3will be high, enabling this gate. This switches R/S F/F number 2,disabling NAND number 2, blocking the output. If, on the other hand,DETECT number 30 COUNTER number 1 NAND is enabled prior to the detectionof shaft encoder number 31, NAND number 3 cannot enable due to the lowinput presented by R/S F/F number 3, and the R/S F/F number 2 outputremains high. This permits output NAND number 2 to enable whenever apulse is received from the comparator. In short, if the shaft encoderpresents readings in the proper sequence,

the auto shut-down circuit does not interfere with the presentation ofcoincidence pulses to counter number 2. If reverse direction of shaftencoder rotation occurs, the auto shut-down circuit permits travelbeyond the next number 59 until it sees number 31 before it sees number30, and shut-down results. Actuating the remote reset push-buttonswitches R/S F/Fs number 1 and number 2, such that each will present ahigh output, and the start-up cycle is repeated.

Referring to FIG. 6: The push-button circuit switches R/S F/Fs number 1and number 2 (FIG. 5), enabling clock pulses and output respectively.This activates the start-up sequence described earlier. The RED LAMP isenergized if either of these two flip flopsare in their shut-down state.

The GREEN LAMP circuit (shown in FIG. 5) contains a monostablemultivibrator that is triggered by the comparator output. This in turn(after amplification) energizes the remote green lamp such that itflashes at a rate consistent with the drilling velocity. Alternatively,the green lamp may be energized by R/S F/F number 2s high output to NANDnumber 2.

Referring to FIG. 7: The COUNTER INCRE- MENTER circuit has twofunctions. First, it reconditions the output from the previous circuitto improve the shape and timing of the pulses fed to the counters, and,secondly, it provides a safeguard against noise during the time that thesystem is in the shutdown state. To re-shape the signal pulses, adifferentiator is followed by a monostable multivibrator. A positivepulse from the MS MV, plus a high output from R/S F/F number 2 (FIG. 5)enables the positive NAND gate, permitting the pulses to reach countersnumber 1 and number 2.

Referring to FIG. 8: The output from the divide by 256 circuit isamplified and fed simultaneously to two differentiators in the READ INCOMMAND AND COUNTER CLEAR circuit. The leading edge differentiatorproduces a positive going pulse directly from the input signal, whilethe trailing edge differentiator includes a PNP transistor to detect thenegatively going trailing edge of the input signal. After amplification,two negatively going pulses are produced one slightly later than theother. The first of these two pulses subsequently transfers the contentsof counter number 2 to the buffer register latches, and the secondclears counter number 2. Considering the output of the divide by 256circuit, this sequence of events occurs once every 30 seconds.

Referring to FIG. 9: The ANALOG RECORDER PAPER ADVANCE circuit accepts apulse from counter number I every time this counter clears from decimal60 to decimal 1. Two pulses per foot of penetration are available fromthis source. These pulses are used to advance the strip chart in theanalog recorder by actuating a relay driven escapement. Circuitry isprovided that permits the user to select, by means of a multi positionswitch on the main frame, the weighting of the chart abscissa.

The usual strip chart has 10 graticule divisions per inch, so(remembering that the pulses from counter number I occur every sixinches of boring bit penetration) the arrangement shown permits theselection of any one of 5, 10, 2O, 40, or feet of penetration per inchof strip chart. The output is such that one pulse moves the strip chartone graticule division with due regard for inertia and coasting of thechart drive mechanism. To accommodate other abscissa weightings, themonostable multivibrator period is adjustable through the use of apotentiometer in the RC relaxation circuit. Further, the flip-flopstring may be increased to accommodate requirements for more compressedabscissa weightings. In short, the system can be supplied with thespecific abscissa weighting scales required in the users application, orhe may select various scales by means of a multi position switch. Anamplifier, in the output circuit, provides an adequate electrical signalto actuate the paper advancing relay.

The remainder of the system circuitry (the Digital to Analog Converter,the integrator, the full-scale deflection selector, the remote digitalread-out, the printer, the BCD serializer, the buffer register, theclock, the analog recorder pen drive mechanism, and the actualcounting/dividing circuits) requires no further elaboration because theyare well known sub-system components in the electronics art. Forexample, we make no claim to the Eccles Jordan FLIP FLOP circuit that isreadily available on the electronics market. To discuss this circuit indetail would not contribute significantly to the system description,because one versed in the art of electronics logic circuitry wouldrecognize that the flip flop circuit, in its many configurations, is oneof the basic tools of the logic designer. The same holds true for suchdevices as NAND and NOR gates, electronic latches in a buffer register,oscillators, and so on.

While there has been described what at present is considered to be apreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the inventive concept disclosed. It istherefore desired that only such limitations be imposed on the appendedclaims as are stated therein.

What is claimed is:

1. A method of determining the magnitude of the linear movement into theearth of a selected element, such as a drill bit, on a drill stringwhich is supported by means vertically movable within a derrick, whereintransient, random linear movement of the drill string does not producesubstantial error in the determination, including the steps of:

transducing the linear movement of the drill string into rotary motion;

transducing such rotary motion into a set of electrical signals whichcumulatively present binary coded words indicative of the direction andangular displacement of the rotary motion,

the binary coded words being presented in a selected and repetitivesequence so long as the rotary motion is caused by the downward movementof the drill string;

monitoring continuously the binary coded words being presented;

producing a count of the binary coded words so long as such binary codedwords are presented in the repetitive, selected sequence and notproducing a count of the binary coded words when they are not presentedin the repetitive, selected sequence; and

once the binary coded words have ceased to be pres- 6 ented m therepetitive, selected sequence, not producing a count of the binary codedwords, even when they are again presented in the repetitive, se-

lected sequence, until the last binary coded word previouslycounted hasagain been presented.

2. A method of determining the magnitude of the linear movement of anelement, such as a drill bit, on a drill string which is supported bymeans vertically movable within a derrick, wherein the transient, randomlinear movement of the drill string does not produce substantial errorin the determination, according to claim 1, wherein the step oftransducing the rotary motion into a set of electrical signalscumulatively presenting binary coded words, includes the steps of:

revolving about an axis a light-interrupting member havinglight-transmitting portions therein; illuminating one side of thelight-interrupting member in a selected pattern; and

sensing on the other side of the light-interrupting member in theselected pattern the illumination which penetrates through thelight-transmitting portions of the light-interrupting member as suchmember revolves.

3. A method for determining the rate of penetration into the earth of aselected element, such as a drill bit, on a drill string supported bymeans vertically movable within a derrick, wherein transient, randomlinear movement of the drill string does not produce substantial errorin the determination, including the steps of:

transducing the linear movement of the drill string into rotary motion;transducing such rotary motion into a set of electrical signals whichcumulatively present binary codedwords indicative of the direction andangular displacement of the rotary motion, the binary coded words beingpresented in a selected and repetitive sequence so long as the rotarymotion is caused by the downward movement of the drill string;monitoring the binary coded words being presented;

producing a count of the binary coded words so long as such binary codedwords are presented in the repetitive, selected sequence and notproducing a count of the binary coded words when they are not presentedin the repetitive, selected sequence;

once the binary coded words have ceased to be presented in therepetitive, selected sequence, not producing a count of the binary codedwords, even when they are again presented in the repetitive, selectedsequence, until the last binary coded word previously counted has againbeen presented;

determining the binary coded words counted in a selected interval oftime; and

comparing the number of binary coded words counted in the selectedinterval of time with the selected interval of time to determine therate of penetration of the element with respect to time.

4. A method for determining the rate of penetration into the earth of aselected element, such as a drill bit, on a drill string which issupported by means vertically movable within a derrick, whereintransient, random linear movement of the drill string does not producesubstantial error in the determination, including the steps of:

transducing the linear movement of the drill string into rotary motion;

transducing such rotary motion into a set of electrical signals whichcumulatively present binary coded words indicative of the direction andangular displacement of the rotary motion, the binary coded words beingpresented in a selected and repetitive sequence so long as the rotarymotion is caused by the downward movement of the drill string;

monitoring the binary coded words being presented;

producing a count of the binary coded words so long as such binary codedwords are presented in the repetitive, selected sequence and notproducing a count of the binary coded words when they are not presentedin the repetitive, selected sequence;

once the binary coded words have ceased to be presented in therepetitive, selected sequence, not producing a count of the binary codedwords, even when they are again presented in the repetitive, selectedsequence, until the last binary coded word previously counted has againbeen presented;

determining from the counted binary coded words when the element hasmoved downward a selected distance;

determining the interval of time required for the drill string to movesuch selected distance downward; and

comparing the selected downward distance moved by the element with thetime interval required for such movement to determine the rate ofpenetration of the element with respect to time during its downwardmovement through the selected distance.

5. In a system for inserting an element, such as a drill string or thelike, into an elongated receiving means, such as a hole being drilled inthe earth, the system including an apparatus for grasping the elementand moving it linearly into the receiving means, a subsystem fordetermining the linear movement of the element into the receiving meanssuch that transient, random linear movement of the element does notintroduce substantial error into the determination, wherein theimprovement comprises:

means for translating the linear movement of the portion of the systemgrasping the element into rotary motion; and

means for translating the direction and angular displacement of therotary motion into a set of electrical signals cumulatively presentingbinary coded words, the binary coded words being in a selected andrepetitive sequence of at least three different binary coded words solong as the rotary motion is in a selected direction;

means for monitoring the binary coded words and producing a count ofsuch binary coded words so long as such binary coded words are presentedin the repetitive, selected sequence and, once the binary coded wordscease to be presented in the repetitive, selected sequence, notproducing a count of the binary coded words, even when they are againpresented in the repetitive, selected sequence, until the last binarycoded word previously counted has again been presented; and

logic means for determining from the counted binary coded words thelinear movement of the element into the receiving means. I

6. In a system for inserting an element, such as a drill string or thelike, into an elongated receiving means, such as a hole being drilled inthe earth, the system including apparatus for grasping the element andinserting it into the receiving means, a subsystem for determining therate of penetration of the element into the receiving means such thattransient random linear movement of the element does not producesubstantial error in the'determination, wherein the improvementcomprises:

means for translating the linear movement of the portion of the systemgrasping the element into rotary motion; means for translating thedirection and angular displacement of the rotary motion into a set ofelectrical signals cumulatively presenting binary coded words, thebinary coded words being in a selected and repetitive sequence of atleast three different binary coded words so long as the rotary motion isin a selected direction; means for monitoring the binary coded words andproducing a count of such binary coded words so long as such binarycoded words are presented in the repetitive, selected sequence, and,once the binary coded words cease to be presented in the repetitive,selected sequence, not producing a count of the binary coded words, evenwhen they are again presented in the repetitive, selected sequence,until the last binary coded word previously counted has been presented;means for determining the number of binary coded words counted in aselected interval of time; and means for comparing the number of binarycoded words counted in the selected interval of time with I the selectedinterval of time to determine the rate of penetration of the elementwith respect to time.

7. In a system for inserting an element, such as a drill string or thelike, into an elongated receiving means, such as a hole being drilled inthe earth, the system including apparatus for grasping the element andinserting it into the receiving means, a subsystem for determining therate of penetration of the elementinto the receiving means such thattransient, random linear movement of the element does notproducesubstantial error in the determination, wherein the improvementcomprises:

means for translating the linear movement of the portion of the systemgrasping the element into rotary motion; means for translating thedirection and angular displacement of the rotary motion into a set ofelectrical signals cumulatively presenting binary coded words, thebinary coded words being in a selected and repetititve sequence of atleast three different binary coded words so long as the rotary motion isin a selected direction; means for monitoring the binary coded words andproducing a count of such binary coded words so long as such binarycoded words are presented in the repetitive, selected sequence and, oncethe binary coded words cease to be presented in the repetitive, selectedsequence, not producing a count of the binary coded words, even whenthey are again presented in the repetitive, selected sequence, until thelast binary coded word previously counted has again been presented;means for determining from the counted binary coded words when theelement has moved a selected distance in the receiving means; means fordetermining the interval of time required for the element to movethrough such selected distance; and

means for comparing the selected distance moved by the element with theinterval of time required for such movement to determine the rate ofpenetration with respect to time during its movement through suchdistance.

8. An apparatus for determining the rate of penetration into a well holeor the like of an element, such as a drill bit, on a drill string whichis attached to a support means movable longitudinally within a derrick,comprising:

ducing the direction and angular displacement of means for monitoringthe binary coded words and producing a count of such binary coded wordsso long as such binary coded words are presented in the repetitive,selected sequence and, once the binary coded words cease to be presentedin the repetitive, selected sequence, not producing a count of thebinary coded words, even when they are again presented in therepetitive, selected sequence, until the last binary coded wordpreviously counted has again been presented;

means for determining from the counted binary coded words when theelement has moved a selected distance in the receiving means,

means for determining the interval of time required for the element tomove through such selected distance; and

means for comparing the selected distance moved by the element with theinterval of time required for such movement to determine the rate ofpenetration with respect to time during its movement through suchdistance.

9. An apparatus according to claim 8 wherein:

the rotating member is opaque and has lighttransmitting portions thereinat selected locations;

the means associated with the rotating member for transducing thedirection and angular rotation of the member into a set of electricalsignals providing binary coded words indicative thereof includes: meansmounted on the one side of the rotating member for illuminating suchside of the member in a selected pattern, and means mounted on the otherside of the rotating member for sensing in the selected pattern theillumination from the light means which penetrates through thelight-transmitting portions of the opaque rotating member as such memberrevolves and for generating a set of electrical signals responsive tothe presence or absence of such illumination.

1. A method of determining the magnitude of the linear movement into theearth of a selected element, such as a drill bit, on a drill stringwhich is supported by means vertically movable within a derrick, whereintransient, random linear movement of the drill string does not producesubstantial error in the determination, including the steps of:transducing the linear movement of the drill string into rotary motion;transducing such rotary motion into a set of electrical signals whichcumulatively present binary coded words indicative of the direction andangular displacement of the rotary motion, the binary coded words beingpresented in a selected and repetitive sequence so long as the rotarymotion is caused by the downward movement of the drill string;monitoring continuously the binary coded words being presented;producing a count of the binary coded words so long as such binary codedwords are presented in the repetitive, selected sequence and notproducing a count of the binary coded words when they are not presentedin the repetitive, selected sequence; and once the binary coded wordshave ceased to be presented in the repetitive, selected sequence, notproducing a count of the binary coded words, even when they are againpresented in the repetitive, selected sequence, until the last binarycoded word previously counted has again been presented.
 2. A method ofdetermining the magnitude of the linear movement of an element, such asa drill bit, on a drill string which is supported by means verticallymovable within a derrick, wherein the transient, random linear movementof the drill string does not produce substantial error in thedetermination, according to claim 1, wherein the step of trAnsducing therotary motion into a set of electrical signals cumulatively presentingbinary coded words, includes the steps of: revolving about an axis alight-interrupting member having light-transmitting portions therein;illuminating one side of the light-interrupting member in a selectedpattern; and sensing on the other side of the light-interrupting memberin the selected pattern the illumination which penetrates through thelight-transmitting portions of the light-interrupting member as suchmember revolves.
 3. A method for determining the rate of penetrationinto the earth of a selected element, such as a drill bit, on a drillstring supported by means vertically movable within a derrick, whereintransient, random linear movement of the drill string does not producesubstantial error in the determination, including the steps of:transducing the linear movement of the drill string into rotary motion;transducing such rotary motion into a set of electrical signals whichcumulatively present binary coded words indicative of the direction andangular displacement of the rotary motion, the binary coded words beingpresented in a selected and repetitive sequence so long as the rotarymotion is caused by the downward movement of the drill string;monitoring the binary coded words being presented; producing a count ofthe binary coded words so long as such binary coded words are presentedin the repetitive, selected sequence and not producing a count of thebinary coded words when they are not presented in the repetitive,selected sequence; once the binary coded words have ceased to bepresented in the repetitive, selected sequence, not producing a count ofthe binary coded words, even when they are again presented in therepetitive, selected sequence, until the last binary coded wordpreviously counted has again been presented; determining the binarycoded words counted in a selected interval of time; and comparing thenumber of binary coded words counted in the selected interval of timewith the selected interval of time to determine the rate of penetrationof the element with respect to time.
 4. A method for determining therate of penetration into the earth of a selected element, such as adrill bit, on a drill string which is supported by means verticallymovable within a derrick, wherein transient, random linear movement ofthe drill string does not produce substantial error in thedetermination, including the steps of: transducing the linear movementof the drill string into rotary motion; transducing such rotary motioninto a set of electrical signals which cumulatively present binary codedwords indicative of the direction and angular displacement of the rotarymotion, the binary coded words being presented in a selected andrepetitive sequence so long as the rotary motion is caused by thedownward movement of the drill string; monitoring the binary coded wordsbeing presented; producing a count of the binary coded words so long assuch binary coded words are presented in the repetitive, selectedsequence and not producing a count of the binary coded words when theyare not presented in the repetitive, selected sequence; once the binarycoded words have ceased to be presented in the repetitive, selectedsequence, not producing a count of the binary coded words, even whenthey are again presented in the repetitive, selected sequence, until thelast binary coded word previously counted has again been presented;determining from the counted binary coded words when the element hasmoved downward a selected distance; determining the interval of timerequired for the drill string to move such selected distance downward;and comparing the selected downward distance moved by the element withthe time interval required for such movement to determine the rate ofpenetration of the element with respect to time during its downwardmovement through the selected distance.
 5. In a syStem for inserting anelement, such as a drill string or the like, into an elongated receivingmeans, such as a hole being drilled in the earth, the system includingan apparatus for grasping the element and moving it linearly into thereceiving means, a subsystem for determining the linear movement of theelement into the receiving means such that transient, random linearmovement of the element does not introduce substantial error into thedetermination, wherein the improvement comprises: means for translatingthe linear movement of the portion of the system grasping the elementinto rotary motion; and means for translating the direction and angulardisplacement of the rotary motion into a set of electrical signalscumulatively presenting binary coded words, the binary coded words beingin a selected and repetitive sequence of at least three different binarycoded words so long as the rotary motion is in a selected direction;means for monitoring the binary coded words and producing a count ofsuch binary coded words so long as such binary coded words are presentedin the repetitive, selected sequence and, once the binary coded wordscease to be presented in the repetitive, selected sequence, notproducing a count of the binary coded words, even when they are againpresented in the repetitive, selected sequence, until the last binarycoded word previously counted has again been presented; and logic meansfor determining from the counted binary coded words the linear movementof the element into the receiving means.
 6. In a system for inserting anelement, such as a drill string or the like, into an elongated receivingmeans, such as a hole being drilled in the earth, the system includingapparatus for grasping the element and inserting it into the receivingmeans, a subsystem for determining the rate of penetration of theelement into the receiving means such that transient random linearmovement of the element does not produce substantial error in thedetermination, wherein the improvement comprises: means for translatingthe linear movement of the portion of the system grasping the elementinto rotary motion; means for translating the direction and angulardisplacement of the rotary motion into a set of electrical signalscumulatively presenting binary coded words, the binary coded words beingin a selected and repetitive sequence of at least three different binarycoded words so long as the rotary motion is in a selected direction;means for monitoring the binary coded words and producing a count ofsuch binary coded words so long as such binary coded words are presentedin the repetitive, selected sequence, and, once the binary coded wordscease to be presented in the repetitive, selected sequence, notproducing a count of the binary coded words, even when they are againpresented in the repetitive, selected sequence, until the last binarycoded word previously counted has been presented; means for determiningthe number of binary coded words counted in a selected interval of time;and means for comparing the number of binary coded words counted in theselected interval of time with the selected interval of time todetermine the rate of penetration of the element with respect to time.7. In a system for inserting an element, such as a drill string or thelike, into an elongated receiving means, such as a hole being drilled inthe earth, the system including apparatus for grasping the element andinserting it into the receiving means, a subsystem for determining therate of penetration of the element into the receiving means such thattransient, random linear movement of the element does not producesubstantial error in the determination, wherein the improvementcomprises: means for translating the linear movement of the portion ofthe system grasping the element into rotary motion; means fortranslating the direction and angular displacement of the rotary motioninto a set of electrical signals cumulatively presentiNg binary codedwords, the binary coded words being in a selected and repetititvesequence of at least three different binary coded words so long as therotary motion is in a selected direction; means for monitoring thebinary coded words and producing a count of such binary coded words solong as such binary coded words are presented in the repetitive,selected sequence and, once the binary coded words cease to be presentedin the repetitive, selected sequence, not producing a count of thebinary coded words, even when they are again presented in therepetitive, selected sequence, until the last binary coded wordpreviously counted has again been presented; means for determining fromthe counted binary coded words when the element has moved a selecteddistance in the receiving means; means for determining the interval oftime required for the element to move through such selected distance;and means for comparing the selected distance moved by the element withthe interval of time required for such movement to determine the rate ofpenetration with respect to time during its movement through suchdistance.
 8. An apparatus for determining the rate of penetration into awell hole or the like of an element, such as a drill bit, on a drillstring which is attached to a support means movable longitudinallywithin a derrick, comprising: a member associated with the derrick andmounted for rotation about an axis; means associated with the drillstring or with the support means for causing the member to rotateresponsive to the linear movement of the drill string, the direction ofthe rotation of the member being responsive to the direction of thelinear movement of the drill string; means associated with the rotatingmember for transducing the direction and angular displacement of themember into a set of electrical signals presenting binary coded wordsindicative thereof, the binary coded words being presented in a selectedand repetitive sequence of at least three different binary coded wordsso long as the rotary motion is responsive to downward movement of thedrill string; means for monitoring the binary coded words and producinga count of such binary coded words so long as such binary coded wordsare presented in the repetitive, selected sequence and, once the binarycoded words cease to be presented in the repetitive, selected sequence,not producing a count of the binary coded words, even when they areagain presented in the repetitive, selected sequence, until the lastbinary coded word previously counted has again been presented; means fordetermining from the counted binary coded words when the element hasmoved a selected distance in the receiving means, means for determiningthe interval of time required for the element to move through suchselected distance; and means for comparing the selected distance movedby the element with the interval of time required for such movement todetermine the rate of penetration with respect to time during itsmovement through such distance.
 9. An apparatus according to claim 8wherein: the rotating member is opaque and has light-transmittingportions therein at selected locations; the means associated with therotating member for transducing the direction and angular rotation ofthe member into a set of electrical signals providing binary coded wordsindicative thereof includes: means mounted on the one side of therotating member for illuminating such side of the member in a selectedpattern, and means mounted on the other side of the rotating member forsensing in the selected pattern the illumination from the light meanswhich penetrates through the light-transmitting portions of the opaquerotating member as such member revolves and for generating a set ofelectrical signals responsive to the presence or absence of suchillumination.